Variable inside Variable? - GameGuru Forum

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Teabone

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Posted: 11th Dec 2019 01:50 Edited at: 11th Dec 2019 02:51

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Hi all,

I'm trying to optimize my code more similar to how i could in other programming languages. Is it possible to have variables be part of other variables?

For instance:

itemID = 1

if item(itemID) + 10 == 100 then
item(itemID) = item(itemID) + 20
end

Is something like that possible or do I have to :

if item1 + 10 == 100 then
item1 = item1 + 20
end

if item2 + 10 == 100 then
item2 = item2 + 20
end

I'm assuming I'll have to use tables for this? Or perhaps its not possible?

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Posted: 11th Dec 2019 10:27

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Circle brackets () are functions in lua, you need to use square brackets [], iow tables/arrays but yes you can use variables as the indexes/pointers.

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AmenMoses

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Posted: 11th Dec 2019 20:39 Edited at: 11th Dec 2019 20:41

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Lists are key/value pairings.

{} - empty list
dlist = { day1 = 'Sunday', day2 = 'Monday' … etc … } - list of days keyed by day1, day2 etc
Prompt( dlist[ 'day1' ] ) - would give you "Sunday"

slist = { 'Sunday', 'Monday' ... etc … } - list without specified key, Lua automatically uses key vales 1, 2 etc
Prompt( slist[ 2 ] ) - would give you "Monday"

Instead of the square brackets you can use . to specify the key so:
Prompt( dlist.day2 ) - would give you "Monday" (I find this form more readable)

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AmenMoses

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Posted: 11th Dec 2019 20:50

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Here is a more useful example:

+ Code Snippet

local my_boats = {}  -- create an empty list

function boat_main( e )

    local boat = my_boats[ e ]   -- create a local pointer to this entities variables

    if boat == nil then   -- if they have not been initialised yet
         my_boats[ e ] =   -- set up the variables with initial values
           {
                state     = 'init',
                timer     = math.huge,
                turnAng   = 0,
                speed     = 80
           }
           return
    end
    -- now for the rest of the function you can reference the variable for a specific boat:
    if boat.turnAng > 20 then 
        -- do something
    end
end

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Posted: 11th Dec 2019 22:56

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What other languages are you familiar with btw?

Lua is a bit special in that it can mimic other languages quite well, for example you can use lists to mimic C structs or Ada records, you can also use them to mimic objects with all the oops bells and whistles if that takes your fancy.

I strongly advise getting hold of "Programming in Lua, fourth edition" and giving it a good read if you haven't already.

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